OSI Layers

The OSI model consists of seven layers each of
which can, and typically does, have several sub layers. The CCNA exam should
not cover any sub layers with the exception of the sublayer for Local Area
Network (LAN) Data Links; the names of the OSI model layers and their main
functions are simply good things to memorize. And frankly, if you want to
pursue your Cisco

certifications beyond CCNA, these names and functional areas
will come up continually.